Points to consider in the practice of postmortem genetic testing: A statement of the American College of Medical Genetics and Genomics (ACMG)

Heritable Burden of Community Sudden Death by Autopsy and Molecular Phenotyping for Precision Genotype Correlation

BACKGROUND

Sudden cardiac death (SCD) genetic studies neglect the majority occurring in older decedents with cardiovascular pathology.

OBJECTIVES

This study sought to determine the burden of genetic disease in unselected adult sudden deaths by precision genotype-postmortem phenotype correlation.

METHODS

The authors used autopsy, histology, and toxicology to adjudicate cause and identify high-suspicion phenotypes (eg, hypertrophic cardiomyopathy) among presumed SCDs aged 18 to 90 years referred to the county medical examiner from February 2011 to January 2018. They tested 231 genes associated with sudden death and correlated genotype with postmortem phenotypes, including myocardial analysis. Family history in high-suspicion phenotype cases was obtained.

RESULTS

Of 856 autopsied presumed SCDs, families of 359 consented and 306 cases (66% cardiac cause) ultimately underwent genetic testing (mean age 62 years, 74% male). Seventy-five cases met high-suspicion phenotype criteria (8.8%), of which 36 underwent testing; 18 families met with a genetic counselor. We found 14 cases with autosomal dominant or X-linked pathogenic/likely pathogenic (P/LP) variants (apparent yield 4.6%); 6 had concordant cause (corrected yield 2%). Yields restricted to autopsy-confirmed cardiac causes (2.5%) and high-suspicion phenotypes (2.7%) were similar. Myocardial genotyping in 14 high-suspicion decedents matched negative blood genotyping, thus did not support somatic mosaicism. Myocardial RNA in a P/LP PKP2 carrier without phenotype demonstrated nonsense-mediated escape as potential mechanism for incomplete penetrance. One-half of high-suspicion cases had a family history of a related condition or sudden death.

CONCLUSIONS

In this 7-year countywide study, 2% of total sudden deaths and 2.5% of confirmed SCDs had identifiable genetic cause, corrected for genotype-phenotype concordance. These results do not support routine genetic testing for community sudden deaths, particularly without autopsy.

A Multidisciplinary Approach to Navigating Variants of Uncertain Significance in Sudden Infant Deaths: A Case Report of 2 Siblings With an SCN10A VUS

ABSTRACT

The sudden death of a previously healthy infant is a devastating event for a family-the death of 2 even more unimaginable. Prior to the debunking of Meadow's law, a legal concept attributing multiple unexplained infant deaths to Munchausen by proxy, these events could lead to the wrongful prosecution of those who had lost their children to "sudden unexpected infant death (SUID)." Today, these cases, wherein multiple infants within one family pass inexplicably, raise suspicion for a possible genetic cause and point toward a need for postmortem genetic testing.We present the case of 2 siblings who passed suddenly in infancy, with no structural cause of death identified at autopsy. Genetic testing in both infants found the same variant of uncertain significance, a heterozygous single nucleotide substitution, denoted c.3191C>T, in SCN10A, which encodes a sodium channel with pathogenic variants possibly implicated in sudden cardiac death syndromes. Although it is unclear at this time if the variant of uncertain significance identified was a contributing factor in the deaths, the case emphasized the importance of involving a multidisciplinary team to ensure appropriate pretest and posttest counseling, interpretation of nuanced testing results, and medical follow-up for surviving family members of SUID.

Cardiac genetic test yields and genotype-phenotype correlations from large cohort investigated by medical examiner's office

BACKGROUND

Few reports describe the yield of postmortem genetic testing from medical examiners' offices or correlate genetic test results with autopsy-confirmed phenotypes from a large cohort.

OBJECTIVES

To report results from cardiomyopathy- and cardiac arrhythmia-associated genetic testing in conjunction with autopsy findings of cases investigated at the United States' largest medical examiner office.

METHODS

Postmortem cases tested from 2015 to 2022 with a cardiomyopathy- and cardiac arrhythmia-associated gene panel were reviewed. American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines were used to classify variant pathogenicity. Correlations of pathogenic/likely pathogenic variants (P/LPVs) with cardiac pathology were evaluated.

RESULTS

The cohort included 1107 decedents of diverse ages and ethnicities. P/LPVs were detected in 87 (7.9%) cases, with 73 and 14 variants in cardiomyopathy and cardiac arrhythmia genes, respectively. Variants of uncertain significance were detected in 437 (39.5%) cases. The diagnostic yield (percentage of P/LPV) in decedents with cardiomyopathy (26.1%) was significantly higher than those without (P<.0001). The diagnostic yield was significantly lower in infants (0.7%) than older age groups (ranging from 1 to 74 years old, 5.7%-25.9%), which had no statistical difference between their yields. The diagnostic yields by cardiac autopsy findings were 54.0% for hypertrophic cardiomyopathy, 47.1% for arrhythmogenic cardiomyopathy, 20.0% for myocardial fibrosis, 19.0% for dilated cardiomyopathy, and 11.3% for myocarditis. Most P/LPVs were in MYBPC3, TTN, PKP2, SCN5A, MYH7, and FLNC. Ten P/LPVs were novel.

CONCLUSIONS

Our results support the importance of performing postmortem genetic testing on decedents of all ages with cardiomyopathy, cardiac lesions insufficient to diagnosis a specific cardiomyopathy (e.g., myocardial fibrosis), and myocarditis. Combined postmortem cardiac examination and genetic analysis are advantageous in accurately determining the underlying cause of death and informing effective clinical care of family members.

Molecular autopsy by proxy: relevance for genetic counseling in rare genetic disorders

Background

Rare genetic disorders may result in death before a definitive clinical diagnosis is established.

Aim

This study aims to outline the processes and challenges in managing, from a genetic perspective, couples who lost children affected by rare genetic disorders.

Results

Six couples who experienced child loss due to rare genetic disorders, seen by the primary author at genetic evaluation and counseling sessions, were retrospectively analyzed. Four out of 6 couples reported consanguinity. Exome and genome sequencing were performed for the parents. Carrier status of two rare lethal metabolic disorders was confirmed in one consanguineous couple. Three couples were carriers of 3 other rare diseases. Variants of LYST, MPV17, HEXB, ITGB4, CD3E, ASPM, TK2, COL11A2, and LAMB3 genes were identified. Six out of 10 were pathogenic variants, out of which 4 correlated with the demised children's phenotypes. One couple was negative for pathogenic variants. The last couple did not undergo genetic testing since they were beyond the fertile window.

Conclusion

Appropriate parental genetic evaluation and counseling are mandatory for selecting the right genetic test to certify the diagnosis postmortem, by virtue of molecular autopsy by proxy. Clarifying a rare disorder diagnosis can help couples to avoid recurrence and plan early for their next pregnancies.

Case report: Novel compound heterozygous IL1RN mutations as the likely cause of a lethal form of deficiency of interleukin-1 receptor antagonist

Undiagnosed monogenic diseases represent a challenging group of human conditions highly suspicious to have a genetic origin, but without conclusive evidences about it. We identified two brothers born prematurely from a non-consanguineous healthy couple, with a neonatal-onset, chronic disease characterized by severe skin and bone inflammatory manifestations and a fatal outcome in infancy. We conducted DNA and mRNA analyses in the patients' healthy relatives to identify the genetic cause of the patients' disease. DNA analyses were performed by both Sanger and next-generation sequencing, which identified two novel heterozygous IL1RN variants: the intronic c.318 + 2T>G variant in the father and a ≈2,600-bp intragenic deletion in the mother. IL1RN mRNA production was markedly decreased in both progenitors when compared with healthy subjects. The mRNA sequencing performed in each parent identified two novel, truncated IL1RN transcripts. Additional experiments revealed a perfect intrafamilial phenotype-genotype segregation following an autosomal recessive inheritance pattern. The evidences shown here supported for the presence of two novel loss-of-function (LoF) IL1RN pathogenic variants in the analyzed family. Biallelic LoF variants at the IL1RN gene cause the deficiency of interleukin-1 receptor antagonist (DIRA), a monogenic autoinflammatory disease with marked similarities with the patients described here. Despite the non-availability of the patients' samples representing the main limitation of this study, the collected evidences strongly suggest that the patients described here suffered from a lethal form of DIRA likely due to a compound heterozygous genotype at IL1RN, thus providing a reliable genetic diagnosis based on the integration of old medical information with currently obtained genetic data.

Postmortem genetic testing in sudden unexplained death: A public health laboratory experience

Sudden unexplained death in the young poses a diagnostically challenging situation for practicing autopsy pathologists, especially in the absence of anatomic and toxicological findings. Postmortem genetic testing may identify pathogenic variants in the deceased of such cases, including those associated with arrhythmogenic channelopathies and cardiomyopathies. The Wisconsin State Laboratory of Hygiene (WSLH) is a state-run public health laboratory which performs postmortem genetic testing at no cost to Wisconsin medical examiners and coroners. The current study examines sequencing data from 18 deceased patients (ages 2 months to 49 years, 5 females) submitted to WSLH, from 2016 to 2021. Panel-based analysis was performed on 10 cases, and whole exome sequencing was performed on the most recent 8 cases. Genetic variants were identified in 14 of 18 decedents (77.8%), including 7 with pathogenic or likely pathogenic variants (38.9%). Whole exome sequencing was more likely to yield a positive result, more variants per decedent, and a larger number of variants of uncertain significance. While panel-based testing may offer definitive pathogenic variants in some cases, less frequent variants may be excluded. Whole exome testing may identify rare variants missed by panels, but increased yield of variants of uncertain significance may be difficult to interpret. Postmortem genetic testing in young decedents of sudden unexplained death can provide invaluable information to autopsy pathologists to establish accurate cause and manner of death and to decedent's relatives to allow appropriate management. A public health laboratory model may be a financially advisable alternative to commercial laboratories for medical examiner's/coroner's offices.